The present invention relates to an electronic musical instrument having waveshape memories for storing musical tone data representing the beginning to the end of musical tones so as to produce high-quality musical tones in accordance with the read out musical tone data.
Nowadays, electronic tone generation is performed such that data of a complete waveshape from the beginning to the end of an actual musical tone waveshape, or data of a leading portion and part of the subsequent portion of the musical tone waveshape are stored. When the complete waveshape data is stored, it is read out to produce a high-quality musical tone signal. However, when the data of the leading portion and part of the subsequent portion are stored, the data of the leading portion is read out, and then the part of the subsequent portion is repeatedly read out to produce a high-quality musical tone signal.
A typical example of a musical tone generation system of this type is described in U.S. Pat. No. 4,383,462. As shown in FIG. 3 of U.S. Pat. No. 4,383,462, a complete is stored in a waveshape memory WM 31, and the waveshape data is read out in response to a KD signal representing a key depression timing. In FIG. 6 of U.S. Pat. No. 4,383,462, three memories WM 61, WM 62 and WM 63 are used. A complete waveshape during an attack period is stored in the WM 61, a musical tone waveshape during at least one fundamental period is stored in the WM 62, and an envelope waveshape from the sustain to decay periods is stored in the WM 63. After the waveshape data is read out from the WM 61 in response to the key depression timing signal KD, the waveshape data are sequentially read out from the memories WM 62 and WM 63.
The system for prestoring the complete waveshape data for a number of periods can easily produce a high-quality musical tone signal. However, a large memory capacity is required. It is very difficult for conventional electronic musical instruments to assign different tone colors to each key touch or pitch. This is because all tone color parameters for each key touch or pitch must be stored in different waveshape memories in units of tone color parameters. As a result, the overall memory capacity becomes very large, resulting in an impractical system.
According to another conventional system, two different waveshapes are interpolated to synthesize a musical tone waveshape. This system is described in U.S. Pat. No. 4,437,379, and realizes key scaling by interpolation between the two different waveshapes. As shown in FIG. 1 of U.S. Pat. No. 4,437,379, a high tone-range waveshape memory 4, a low tone-range waveshape memory 5 and a reference tone range memory 3 store high tone-range waveshape data, low tone-range waveshape data and reference tone-range waveshape data, respectively. One of the high and low tone-range waveshapes is selected by a selector 7 by determining whether a tone-range of a depressed key is a higher or lower range than the reference tone range. For example, when a player depresses a key falling within the range between the high tone-range waveshape and the reference tone-range waveshape, the high and low tone-range waveshapes are interpolated to produce a tone waveshape corresponding to the difference between the depressed key belonging tone range and the reference tone range. However, according to U.S. Pat. No. 4,437,379, the high, low and reference tone-range waveshapes are the musical tone waveshapes for specific periods and are repeatedly read out until the musical tone decays. As a result, a musical tone of sufficiently high quality cannot be produced.